"Any war" is a pretty steep challenge just given the instability in parts of Latin America, but any war outside the Western Hemisphere is not really too difficult. The two main things to achieve are no US colonies outside of that area, very easy, and simply no major wars that drag the US in, fairly easy. OTL WW1 was far from guaranteed to occur, and is quite easy to avoid even risking with a PoD in 1865.
The long term trends in Europe prior to WW1 were increasing economic and social integration, as well as democratic maturation all of which reduce the likelihood of conflict and which taken together with no major crises that step on the toes of the great powers could avoid war in Europe. Without European war Japan would never have a chance to do what it did in Asia, while Russia reforming along Western European lines is quite plausible. None of this makes war impossible by any stretch, but it does make avoiding it fairly easy. Without Eurasia plunging into the abyss, the US would have no need to intervene in major conflicts and with Western European power intact no need to intervene in minor conflicts, as a no-war Western Europe would remain far more influential on the world stage.